Most #cars use #brake fluid because it's a #critical component of a #hydraulic braking system. The brake #fluid transfers #pressure from the brake #pedal to the #calipers or #wheel cylinders, pushing the brake #pads against the #disc or #drum to slow down or stop the #vehicle. A slow drop in brake fluid over weeks or months is often a #sign of worn brake pads. As the brake pads wear thinner, the caliper #pistons need to extend further to reach them, which means more brake fluid is drawn into the #caliper to compensate for the increased distance. A #rapid drop in brake fluid, especially within 1–3 days, is usually a sign of a #leak in the system. This is #dangerous. A leak can cause a sudden loss of braking pressure, leading to brake #failure. Do not drive the vehicle. Inspect the brake system immediately or have a #mechanic do a full check and repair. Brake fluid is #hygroscopic, meaning it absorbs #moisture from the #air over time. This reduces its #boiling point, which can lead to #vapor lock (formation of air bubbles), making your brakes feel spongy or even fail under heavy use. Recommendation: Replace brake fluid every 2 years or according to your vehicle #manufacturer’s maintenance schedule.